1. Field of the Invention
The present invention relates to multilayer multicolor photographic materials and particularly to incorporated-dye image forming coupler type multilayer multicolor photographic materials having improved image sharpness.
2. Description of the Prior Art
Incorporated-dye image forming coupler type multilayer multicolor photographic materials generally have three silver halide emulsion layers each having a different sensitivity range which form dye images corresponding to blue, green and red light on a support. In the silver halide emulsion layers, a large number of silver halide crystals having a particle size nearly corresponding to the wavelength of visible light is randomly dispersed in a binder such as gelatin. Therefore, even if visible light passes perpendicularly into the emulsion layers, the light is scattered by silver halide particles and spreads out in the direction of the plane of the emulsion layers. This phenomenon causes a blurring of the images formed. This is an important problem from the standpoint of image reproduction since the sharpness of dye images formed on the photographic material is deteriorated. This becomes more important where the images are enlarged for observation. Therefore, many attempts have been made hitherto for the purpose of improving the sharpness of images.
One attempt is to position a green-sensitive silver halide emulsion layer for forming a magenta dye image as the photosensitive layer nearest the surface. This is because the human eye is the most sensitive to differences in brightness modulated by the magenta image. This attempt, however, causes an undesirable result in that light to be recorded only by a blue-sensitive silver halide emulsion layer is recorded by the green-sensitive layer as the top layer, because silver halide is inherently sensitive to blue light.
Further, a method is known which comprises using colored materials such as a dye in order to absorb scattered rays. However, this method has the defect that the sensitivity is deteriorated.
Another attempt is a method which comprises reducing the thickness of the photographic emulsion layers. For example, a method of decreasing the ratio of the binder to the silver halide is known. However, a substantial decrease of the binder in the emulsion results in a deterioration of the quality of the film to result in a restriction of the quantity of the dye image forming coupler which can be incorporated. This is particularly a defect where the dye image forming coupler is introduced into the silver halide emulsion layer together with a solvent having a high boiling point.
Accordingly, it has been desired to provide a new process for improving the sharpness of images in incorporated-dye image forming coupler type multilayer multicolor photographic materials.